Roger Federer was congested but not tested. Speaking through the nasal twang of a flu that made its way through the entire Federer clan and eventually claimed its patriarch, the Swiss great said he was on the mend as he tries to defend his Brisbane International title.

The world number three needed only 55 minutes and a few Codrals to dismiss the challenge of German qualifier Tobia Kamke on Thursday night, ensuring he was tucked up in bed nice and early after a 6-2 6-1 rout.

He will meet Bulgarian Grigor Dimitrov in the quarter-final on Friday night but much of the conjecture before his first appearance of 2016 focused on reports of a health or injury scare that could have potentially scuttled his tournament.

As it turns out, that ailment was a nasty flu, hence Federer's request to put his opening match back to Thursday, which means he now has to play on four consecutive days if he makes Sunday's final.

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In good shape: Roger Federer stretches for a forehand against Tobias Kamke.Credit:AP

He knew it was coming, too, after it had made its way through his family. He didn't feel well enough to hit-up on Tuesday but was convinced he would be fine by Wednesday, particularly given the calibre of his opponent, ranked 233 in the world.

"I was going to take Monday off and then on Tuesday I was going to hit in the afternoon but I didn't feel so well. So I said, 'let's wait it out'. Then didn't feel good at all on the Tuesday," Federer said.

"On the Wednesday I started to feel a little bit better, so I asked the tournament if they could move it for a Thursday start, which I know they can do very easily, which was helpful.

"So started to feel a little bit better. That's why I came out yesterday (Wednesday) for a hit, just to see how things are. I was happy. I felt somewhat okay. There was no need to push it at all. I am not somebody that needs to play much before matches.

"I'm quite surprised that it went so well today."

He went swimmingly, in fact. And despite his obvious symptoms, it would have taken Federer to get hit by one of the nearby freight trains that frequently rumble past Pat Rafter Arena to keep him out of action.

Kamke serves to Federer.Credit:Getty Images

At 34, Federer remains one of the most durable athletes on the tour. In his entire career, he has never retired from a match and has now played in 64-consecutive Grand Slams.

Granted, Brisbane doesn't quite stack up against the majors and he did concede that on another occasion, in another city, against another opponent over five sets, he may have felt different.

As it was, he took care of business like the ultimate professional he is and even surprised himself with the clinical nature of his performance.

He now meets Dimitrov at the same venue on Friday night, with the Bulgarian progressing earlier in the day with a three-set win over Serbian Viktor Troicki.